<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>float</title>
    <style>
      * {
        margin: 0;
        padding: 0;
      }
      .container {
        width: 100%;
        height: 100vh;
      }
      .left{
        float: left;
        width: 100px;
        height: 100%;
        background: lightblue;
      }
      .right{
        float: right;
        width: 100px;
        height: 100%;
        background: lightblue;
      }
      .main{
        height: 100%;
        margin: 0 100px;
        background: lightpink;
      }
    </style>
  </head>
  <body>
    <div class="container">
      <div class="left"></div>
      <div class="right"></div>
      <div class="main"></div>
    </div>
  </body>
</html>
